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Biomedical subjects

J Schmitz

Publications and source records attributed to J Schmitz.

At least 145 records · Page 8Linked to original sources
PubMed1993

Optimizing follicular dendritic cell isolation by discontinuous gradient centrifugation and use of the magnetic cell sorter (MACS).

Follicular dendritic cells (FDC) contribute minimally to the total cell population of lymphatic tissue. In order to obtain higher numbers of viable FDC with only a small fraction of contaminating cells the following procedure was developed. Subsequent to the usual mechanical and enzymatical digestion of human tonsils, single cells were layered on top of a discontinuous bovine albumin gradient and centrifuged at 8500 x g. The suspension collected from the 1.052-1.030 interphase contained an average of 10.5% FDC. Next, the preparation was subjected to a new step involving separation of FDC previously treated with biotin-labelled KiM4 monoclonal antibody, raised against FDC, and attached via biotin-streptavidin bonding to streptavidin-conjugated paramagnetic beads. Purification on a magnetic cell sorter (MACS) yielded 3.3-10.1 x 10(6) cells with an average FDC content of 78.4%. The viability and morphology of the resulting FDC population was examined using trypan blue staining or electron microscopy. This technique will permit in vitro studies and long term cultures with FDC isolated from human lymphatic tissue.

Antibodies, Monoclonal↗
PubMed1993

Regulation of T helper cell cytokine expression: functional dichotomy of antigen-presenting cells.

A bias to either cell-mediated or antibody-mediated effector mechanisms is induced in an immune response against a pathogen, if activated T helper cells (Th) predominantly express Th1 [interleukin (IL)-2, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-beta] or Th2 (IL-4, IL-5, IL-6 and IL-10) cytokines. Here we provide evidence that, due to the capability to secrete IL-1, macrophages, but not B cells, as antigen-presenting cells (APC) induce production of IFN-gamma in resting Th cells. Normal murine splenic Th cells were activated in vitro with the superantigen Staphylococcus aureus enterotoxin B (SEB) presented by macrophages as compared to other APC from murine spleen. As determined by immunofluorescence, Th cells producing IL-2 but almost none producing IL-4 and IL-5 are generated, irrespective of the type of APC. Generation of IFN-gamma-producing Th cells is largely dependent on presentation of SEB by macrophages. The requirement for macrophages, however, is overcome if IL-1 is provided. Expression of IFN-gamma by Th cells is not induced, if production of IL-1 by macrophages is inhibited by IL-10. Our results suggest a functional dichotomy of APC: normal resting Th cells differentiate into IL-2 and IFN-gamma secreting cells (Th1 cells) if antigen is presented by macrophages, whereas presentation by B cells generates Th cells secreting IL-2, which might differentiate into Th2 cells upon re-stimulation.

Animals↗
PubMed1993

Mutational analysis of the nucleic acid-binding 17 kDa phosphoprotein of potato leafroll luteovirus identifies an amphipathic alpha-helix as the domain for protein/protein interactions.

The 17 kDa protein (pr17) of potato leafroll luteovirus is translated from a subgenomic PLRV RNA by internal translation initiation and binds to single-stranded nucleic acids (E. Tacke, D. Prüfer, J. Schmitz, and E. Rohde, 1991, J. Gen. Virol. 72, 2035-2038). Chemical crosslinking of in vitro expressed pr17 provided evidence for the preferential formation of pr17 homodimers which were also detected in PLRV-infected potato plants and isolated from potato lines expressing the PLRV pr17 transgene. Mutation analysis identified an amphipathic alpha-helix within the acidic amino-terminus of pr17 which acts as the domain for protein/protein interactions. Pr17 was predominantly associated with subcellular fractions enriched for nuclei, chloroplasts, mitochondria, and membranous structures. In addition it was shown that pr17 was phosphorylated in planta and that this modification did not inhibit binding of the protein to nucleic acids.

Amino Acid Sequence↗
PubMed1993

Numbers of T cell receptor (TCR) alpha beta+ but not of TcR gamma delta+ intraepithelial lymphocytes correlate with the grade of villous atrophy in coeliac patients on a long term normal diet.

Numbers of T cell receptor (TcR) gamma delta+ and alpha beta+ intestinal lymphocytes were studied in 34 coeliac patients in respect of their diet and the grade of villous atrophy. Particular attention was given to a group of 21 patients with coeliac disease according to ESPGAN criteria who were on a well tolerated long term normal diet and in nine of whom the mucosa had returned to normal or nearly normal. A significant increase in TcR gamma delta+ cells was observed in the gut epithelium of coeliac patients compared with age matched controls, and this did not correlate with either the presence of gluten in the diet or with the grade of villous atrophy. Thus, numbers of TcR gamma delta+ intraepithelial lymphocytes (IEL) were considerably above the normal range in four of seven patients on a gluten free diet and in four of nine patients who had recovered a normal or nearly normal mucosa in spite of a normal diet. In contrast, numbers of intestinal TcR alpha beta+ cells varied with the stage of the disease. Their number was high in the epithelium of patients with active coeliac disease (n = 18) but significantly less in patients whose mucosa had returned to normal or nearly normal either after gluten free diet (n = 7) or in spite of a normal diet (n = 9). Immunohistochemical markers of intestinal mononuclear cell activation detected in active coeliac disease were either weakly expressed or absent in the latter patients. It is suggested that TcR alpha beta+ but not TcR gamma delta+ IEL are sensitised to gliadin in coeliac disease, and that only the former cells play a direct part in the pathogenesis of the villous atrophy. The normal counts of TcR alpha beta+ IEL and the absence of detectable mononuclear activation in the biopsy specimens of a few patients who have recovered clinical and histological tolerance to gluten sustains this hypothesis and also suggests that immunological tolerance to gluten may be acquired in a subgroup of coeliac patients. Hte appreciable increase in TcR gamma delta+ IEL observed in some of the latter patients, however, is similar to that observed in latent coeliac disease urging for their careful and prolonged follow up until the role of TcR gamma delta+ IEL in the pathogenesis of coeliac disease is elucidated.

Adolescent↗
PubMed1993

Substance abuse among subjects screened out from an alcoholism research program.

Three hundred and eight subjects were screened over the phone for admission to an inpatient alcohol treatment research unit. Using a structured interview, the prospective patients were asked questions regarding demographics, drinking history, previous treatments, physical health, family history, and a detailed history of past and present substance use. Drug use was studied as regular use versus no use or brief experimental use of five drug categories: cannabinoids, stimulants, sedatives, opiates, and hallucinogens. Fifty-one percent of the men and 48% of the women reported regular use of one or more of the drugs in addition to alcohol. For women, the amount of alcohol intake was positively correlated with use of stimulants (r = .32, p = .001), cannabinoids (r = .24, p = .019), sedatives (r = .30, p = .003), and hallucinogens (r = .30, p = .003). For men, correlations between the amount of alcohol intake and drug use were weaker but significant for stimulants (r = .21, p = .002), opiates (r = .15, p = .028), and hallucinogens (r = .15, p = .029). Women with alcoholic mothers displayed higher alcohol intake than women with nonalcoholic mothers (p = .02) and also showed more frequent use of most drugs. Although men with alcoholic fathers also showed greater alcohol intake compared to men with nonalcoholic fathers, the two groups did not differ in drug use. Younger subjects of both sexes were more likely to use cannabinoids, stimulants, opiates, and hallucinogens. Alcohol and sedative use was relatively constant across all age groups.

Adult↗
PubMed1993

Human Kupffer cells infected with HIV-1 in vivo.

Blood monocytes as well as cells of the macrophage-phagocytic system in several tissues are targets for HIV-1 in vivo and in vitro. However, the data on HIV-1 infection of liver macrophages/Kupffer cells (KCs), which make up the main pool of fixed-tissue macrophages, is controversial. We therefore studied HIV-1 infection of KCs in vivo. Blood and liver tissue was obtained from seven AIDS patients shortly after death. Liver tissue was minced before processing. Cell suspensions were further purified by density gradient centrifugation, stained with anti-CD14 (blood monocytes) or anti-macrophage 25F9 (KCs), and separated by fluorescence-activated cell sorting (FACS). These highly purified cell populations were then analyzed for HIV-1 proviral DNA by the polymerase chain reaction (PCR). By performing PCR on FACS-purified cell populations, we could show that both KCs and peripheral blood monocytes were HIV-1-infected in 3 of 7 patients. KCs harbored HIV-1 proviral DNA only if peripheral blood monocytes were infected. These data show that KCs of the liver are infected with HIV-1 in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Absence of microsomal triglyceride transfer protein in individuals with abetalipoproteinemia.

Abetalipoproteinemia is a human genetic disease that is characterized by a defect in the assembly or secretion of plasma very low density lipoproteins and chylomicrons. The microsomal triglyceride transfer protein (MTP), which is located in the lumen of microsomes isolated from the liver and intestine, has been proposed to function in lipoprotein assembly. MTP activity and the 88-kilodalton component of MTP were present in intestinal biopsy samples from eight control individuals but were absent in four abetalipoproteinemic subjects. This finding suggests that a defect in MTP is the basis for abetalipoproteinemia and that MTP is indeed required for lipoprotein assembly.

Abetalipoproteinemia↗
PubMed1992

Effects of brief early exposure to partially hydrolyzed and whole cow milk proteins.

Clinical experience ("the dangerous bottle") and experimental evidence indicate that the early life of an infant is particularly important for the development of the immune responses to food antigens. However, the clinical and immunologic consequences of a brief exposure to, or avoidance of, food antigens during the neonatal period in human infants are poorly understood and documented. We present the preliminary results of a prospective controlled study of 256 normal breast-fed infants randomly assigned to receive (blind) either an adapted formula (Nidina) or a partially hydrolyzed formula (Nidal HA) as a supplement to breast-feeding for a few days when necessary, and to be examined at days 5, 90, 150, and 365. The results indicated that (1) the prevalence of clinical symptoms and of total and specific IgE responses was not statistically different in the two groups of infants and (2) infants fed a hydrolyzed formula had median titers of specific IgG lower than those fed an adapted formula; the difference was significant for alpha-lactalbumin at day 90 (p < 0.005) and for alpha-lactalbumin (p < 0.05), casein (p < 0.05), and hydrolyzed formula (p < 0.01) at day 150. Humoral immune responses of breast-fed infants to food antigens thus appear to be modulated by early, short-term exposure to them.

Breast Feeding↗
PubMed1992

Distinct antigen presenting cell-derived signals induce TH cell proliferation and expression of effector cytokines.

In addition to the stimulus delivered by the specific interaction of the T cell receptor (TCR) and the antigen - MHC class II complex, activation of resting helper T lymphocytes (TH) requires several poorly defined accessory cell-derived co-stimulatory signals. Here we provide evidence that proliferation and expression of effector cytokine genes by TH cells are induced by distinct co-stimulatory signals. Normal murine splenic TH cells were activated by Staphylococcus aureus enterotoxin B (SEB) superantigen and various antigen presenting cells (APCs) to proliferate, differentiate into TH cells blasts, and secrete cytokines. Blast transformation and proliferation of TH cells is achieved with macrophages and other splenic APCs, like B cells. Expression of the cytokines interferon gamma (IFN gamma), IL-5, and IL-2 by TH cells, however, is to various degrees dependent on the presentation of SEB by macrophages. The requirement for macrophages is particularly striking for the expression of IFN gamma. Thus macrophages provide distinct co-stimulatory signals for cytokine secretion and proliferation. The results suggest that B cells induce clonal expansion of TH cells whereas macrophages additionally promote terminal differentiation of activated TH cells into TH effector cells.

Animals↗
PubMed1992

Proliferation of non-Hodgkin-lymphoma lymphocytes in vitro is dependent upon follicular dendritic cell interactions.

Follicular dendritic cells (FDC) are located within the B-cell follicles of non-malignant lymphatic tissues and within non-Hodgkin-lymphomas (NHL) derived from the germinal centre or the mantlezone. The interactions between FDC and non-neoplastic B-cells have been extensively investigated but so far no data on functional studies with FDC isolated from lymphoma tissue are available. Using an enzyme cocktail to digest lymph nodes from patients with NHL followed by density centrifugation, single cell suspensions enriched in FDC and B-lymphocytes were obtained. In these preparations FDC formed small cellular clusters with an average of five neoplastic lymphocytes for every FDC. Immunocytochemistry with Ki67 revealed that after 24 h of culture 23.7% of the cells within the clusters were in late G1 to M phase. In contrast, only 10.2% of the lymphoma cells scattered outside the clusters were in these activated stages. As visualized by autoradiography, after 72 h of incubation the rate of proliferation was 16.8 times higher for the lymphoma cells involved in cluster formation as compared to those lymphocytes not associated with FDC. The data indicate that in vitro FDC from NHL lymph nodes form a microenvironment favourable for the activation and proliferation of lymphoma cells. The search for cytokines secreted by FDC in lymphoma tissue is under way.

Aged↗
PubMed1992

Follicular dendritic cells in non-Hodgkin-lymphoma express adhesion molecules complementary to ligands on neoplastic B-cells.

In non-Hodgkin-lymphoma (NHL) with nodular growth patterns, follicular dendritic cells (FDC) form a spherical network which contains neoplastic B-cells. In order to dissect the basis of this close FDC/B cell association, the antigenic profile of adhesion molecules expressed by individual FDC and NHL-B-lymphocytes was evaluated. FDC isolated from NHL were found to express C3bi receptors (CD11b), the very late antigen (VLA) alpha-5- and alpha-6-chain (CD49e, CD49f), and the intercellular adhesion molecule-1 (ICAM-1; CD54). Only a percentage of the FDC population was positive for the VLA beta-1- and alpha-3-chain (CD29, CD49c), the vitronectin receptor (CD51) and the vascular cell adhesion molecule-1 (VCAM-1). B-cells obtained from the lymph nodes of patients with centroblastic-centrocytic lymphoma expressed several ligands complementary to the adhesion molecules detected on FDC. These include LFA-1 alpha- and beta-chains (CD11a, CD18), and ICAM-1 (CD54). Surprisingly, monoclonal lymphocytes in the peripheral blood of patients with a leukaemic course of this lymphoma entity were devoid of these antigens. It seems likely then that neoplastic B-cells without CD11a, CD18 and CD54 surface molecules are unable to associate with FDC and now invade other compartments. Thus, the adhesive interactions which do occur between FDC and NHL-B-cells may directly influence the peculiar growth pattern and spread of centroblastic-centrocytic lymphoma.

Antibodies, Monoclonal↗
PubMed1992

The effect of alcohol withdrawal on serum concentrations of Lp(a), apolipoproteins A-1 and B, and lipids.

Moderate alcohol consumption is associated with a decreased risk of coronary artery disease. The mechanism of the putative protective effect of alcohol intake, however, remains elusive. Recent studies suggest that a ratio of apolipoprotein A-I/apolipoprotein B and Lp(a) are better indicators of the risk of atherosclerosis than total cholesterol and high density lipoprotein cholesterol. To assess the effect of alcohol on these analytes, we determined the concentration of Lp(a), apolipoprotein A-I, apolipoprotein B, total cholesterol, and high-density lipoprotein cholesterol, and calculated low-density lipoprotein cholesterol in serum of 12 patients meeting DSM-III-R criteria for alcohol dependence at the time of admission for treatment of alcohol withdrawal (before). The analyses were repeated after 4 weeks of supervised abstinence on a locked research unit (after). With abstinence, there was a significant increase in the concentration of Lp(a), the atherogenic index and the ratio of low-density to high-density lipoprotein cholesterol but a significant decrease in total cholesterol, high-density lipoprotein cholesterol, apolipoprotein A-I, and the apolipoprotein A-I/B ratio. Apolipoprotein B and low-density lipoprotein cholesterol showed no significant changes before and after alcohol abstinence. Thus, decreased Lp(a) and increased high-density lipoprotein cholesterol and apolipoprotein A-I may be factors mediating the putative protective effect of alcohol in coronary artery disease.

Adult↗
PubMed1992

Malnutrition in Crohn's disease: substrate deficiency or misuse?

Growth failure is frequently associated with Crohn's disease. However, it does not seem to be fully accounted for by overt endocrinological abnormalities or nutrient deficiencies. It may be related to an abnormal utilization of available substrates, particularly proteins, due to an imbalance in protein metabolism kinetics. Its primary mechanism may be an increase in protein breakdown rates over synthesis, specifically related to the associated inflammatory syndrome, and progressively leading to a protein debt. Reduction in food intake would only exaggerate this trend by further reducing the synthesis to breakdown ratio, whereas nutrient supplementation merely compensates for the deficit by promoting protein synthesis.

Child↗